Multi-lateral wells have a vertical bore with two or more lateral windows therealong, each window communicating with a respective lateral bore. In order to access a lateral bore, it is typically necessary to run a coiled tubing string into the well three times.
For example, in order to direct a tool into a selected lateral bore, the coiled tubing string is run into the well with a whipstock thereon, and the whipstock is then fixed at the lower end of the window for the selected lateral bore. Then, the tubing string is withdrawn, leaving the whipstock in place. Thereafter, the coiled tubing string is run into the well a second time, with the appropriate tool at the end of the tubing string. When the tool reaches the whipstock, the whipstock deflects the tool out into the selected lateral bore. When use of the tool is completed, the coiled tubing string is withdrawn again in order to remove the tool from the well. Subsequently, the coiled tubing string is run into the well a third time, with a retrieving device which can engage a fishing neck provided on the whipstock. Then, the coiled tubing string is withdrawn from the well, in order to retrieve the whipstock out of the well.
During this three-trip procedure, the coiled tubing string is uncoiled three times for respective insertions, and is coiled back up three times during respective withdrawals. Coiling and uncoiling the tubing string contributes to fatigue and ultimate failure of the tubing string, which is relatively expensive. Thus, it is highly desirable to reduce the number of insertions or trips of the coiled tubing string into the well in order to perform any desired operation, including insertion and retrieval of a tool from a lateral bore.